Fix compiling on gcc-4.6....

ppapi/proxy/ppb_context_3d_proxy.cc

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ppapi/proxy/ppb_context_3d_proxy.h"
 
 #include "base/hash_tables.h"
 #include "gpu/command_buffer/client/gles2_cmd_helper.h"
 #include "gpu/command_buffer/client/gles2_implementation.h"
 #include "ppapi/c/pp_errors.h"
@@ skipping 377 matching lines @@
     return true;
 
   last_state_.error = gpu::error::kLostContext;
   return false;
 }
 
 Context3D::Context3D(const HostResource& resource)
     : PluginResource(resource),
       draw_(NULL),
       read_(NULL),
-      transfer_buffer_id_(NULL) {
+      transfer_buffer_id_(0) {
 }
 
 Context3D::~Context3D() {
   if (draw_)
     draw_->set_context(NULL);
 }
 
 bool Context3D::CreateImplementation() {
   PluginDispatcher* dispatcher = PluginDispatcher::GetForInstance(instance());
   if (!dispatcher)
@@ skipping 191 matching lines @@
                                                    &shm_handle,
                                                    &shm_size)) {
     return;
   }
   *transfer_buffer = TransportSHMHandleFromInt(dispatcher(), shm_handle);
   *size = shm_size;
 }
 
 }  // namespace proxy
 }  // namespace pp